1. Field of the Invention
The invention relates to methods and apparatuses for repairing conduits. More particularly, the invention is directed to methods and apparatuses for repairing damaged, weakened, or leaking conduits that are located in areas to which it is difficult to gain access, for example, sewer pipes, water mains, wells, and gas lines.
2. Background Information
Over a period of time, conduit systems for carrying water or wastewater become damaged, weakened, or otherwise begin to deteriorate and leak at the joints between adjacent sections. Such deterioration is caused by the settling of the surrounding earth adjacent the conduit system, by deterioration of the joints themselves over time, and/or by the growth of roots from trees and other plants.
In wastewater systems, wastewater can begin to leak out from damaged conduits and create problems of pollution. In addition, damaged sections can have a groundwater infiltration problem which increases the volume of water carried to the treatment facility, thereby overburdening it.
Further, deteriorated conduits for liquid conveyance systems, including sewer systems that result in leaks can soak the surrounding terrain, sometimes creating sinkholes and exacerbating drainage problems. Further, support for buildings, bridges, for example, provided by the terrain in which a leaking conduit is located, can become weakened, thereby risking additional property damage or more serious concerns including loss of life.
A variety of solutions to the problem of repairing buried conduit sections have been proposed in the art. The most common solution involves excavation around the damaged conduit section and either the repair or replacement of the damaged section. However, excavation is time-intensive and, particularly in urban areas, it creates additional problems.
Methods have also been developed for repairing a damaged conduit section from within and without the need for excavation. Such methods include simply the application of a grout material for sealing cracks and joints, for example. It is also known in the art to re-line damaged conduit sections with a liner that is expanded from a coiled configuration to a final configuration in which the liner is secured against the inner surface of the damaged conduit section.
Above-mentioned “no-dig” methods and apparatuses are disclosed, for example, in U.S. Pat. Nos. 5,119,862; 5,351,720; and 5,465,758, the disclosures of which are incorporated by reference thereto in their entireties.
Furthermore, in the repair of relatively high-pressure pipes and conduits, such as natural gas lines and water lines, there is usually a need to shut down a line, relieve pressure, and take it out from service. The same operations should be done for different periodic maintenance after repair as well.
Additional problems could be built up by external pressure exerted by a relatively high water level difference, such as in the case of water well exploitation. Similar problems could happen in the case of an external environment or internal fluid temperature changes.
Above-mentioned pressure or temperature changes cause diameter changes in the host pipe, and as a result, a certain gap between host pipe and repair sleeve can be formed. For instance, it has been known that an HDPE (High Density Polyethylene) pipe with an original internal diameter of 29 inches can increase in diameter up to 29.23 inches under a standard working pressure of 150 psi.
U.S. Pat. No. 6,138,718, the disclosure of which is hereby incorporated by reference thereto in its entirety, only partially solves this “gap problem.” Methods and apparatuses disclosed in this patent can compensate for a nascent gap at the time of installation and for a certain short time thereafter. The reason for the subsequent failure relates to the fatigue of some materials, for instance, closed-cell plastic foam exposed to pressure loses in the gas enclosed within the cells. Another reason of the subsequent failure appears when the certain working pressure is applied to the host pipe, as well as to the self-locking sleeve, and unlocks it. For the same HDPE pipe, the increase circumference by ⅛ inch (3.175 mm) causes the sleeve to unlock, and it might happen at a pressure of 26 psi or an internal fluid temperature rapidly dropping by 78° C. (in the case of a stainless steel sleeve).
A similar problem appears in the case of the gap between a rigid host pipe and an installed CIPP (Cured-In-Place-Pipe) liner. This gap varies under an operating pressure, and as a result, any known sealing means at the ends of the CIPP liner will be destroyed.